The present invention relates to vibration damping devices, and more particularly, to rotary dampers for use in automotive vehicle shock absorbing systems.
Automobiles and other vehicles utilize shock absorbers to dissipate shock and vibrational forces sustained by the vehicle wheels. The vehicles typically use conventional, linear-style shock absorbers. Such shock absorbers may include a pair of telescoping cylindrical sleeves oriented generally vertically in the vehicle. A piston is attached to one of the sleeves and travels in a fluid-filled cylinder associated with the other sleeve. One of the sleeves is coupled to a wheel support structure of the associated vehicle and the other sleeve is attached to the frame of the vehicle. When shock or vibrational forces displace the associated vehicle wheel relative to the associated vehicle, the force drives the piston along the cylinder, thereby forcing fluid through an orifice in the piston, which resists such motion with a force proportional to the shock force. In conventional shock absorbers, the shock absorber must extend between the vehicle body and wheel support structure, and must be oriented along the direction of travel of the wheel support structure in response to a shock load. Therefore, the conventional linear-style shock absorber is limited in its spatial orientation.
Rotary shock absorbers, or rotary dampers, have been developed to replace linear-style shock absorbers. Rotary shock absorbers have several advantages over conventional linear-style shock absorbers and operate by converting shock forces into rotary motion, and then damping the rotary motion. For example, rotary shock absorbers are not limited in spatial orientation relative to the vehicle body to oppose shock forces, as are linear-type shock absorbers. Rotary dampers may be oriented generally horizontally, and thereby extend underneath the body of the associated vehicle. Furthermore, because the rotary damper is more isolated from the vehicle frame than conventional linear-type shock absorbers, shock and vibrational forces (including noise) are not transmitted from the shock absorber to the vehicle body to the same extent as prior art linear-style shock absorbers.
Rotary dampers typically include a shaft, arm, or cam which transmits shock forces from the wheel to one or more components that are forced through a fluid filled chamber to damp the shock forces. However, existing rotary dampers can be relatively large, lack durability, and be expensive to manufacture. Accordingly, there is a need for a rotary damper that is compact, durable, and inexpensive.
The present invention is a rotary damper, suitable for use in an automotive vehicle shock absorbing system, which is compact, robust and relatively inexpensive to fabricate. The rotary damper of the present invention includes a rotatable cam coupled to a pair of pistons, each mounted in its own fluid-filled orifice and coupled to opposite sides of the cam such that rotation of the cam causes the pistons to move within their respective piston orifice. The movement of the pistons in the piston orifices in response to movement of the cam forces the fluid through a set of valves, which damps the applied forces.
In a preferred embodiment, the damper includes an outer casing enclosing a main chamber and a pair of piston orifices filled with a damping fluid. A pivotable cam is located in the main chamber and is attached to an arm which typically is connected to a wheel support structure. The damper also includes a pair of pistons, each located in one of the pair of orifices and connected to opposed sides of the cam. The arm is connected to pivot about its connection to the cam. Movement of the arm pivots the cam within the main chamber, which moves each piston in opposite directions in its respective piston orifice. Displacement of the piston forces fluid through orifices in the pistons which damps the rotary movement of the arm.
Other objects and advantages of the present invention will be apparent from the following description, the accompanying drawing and the appended claims.